The long term objective of the proposed program is to develop optical and electrochemical sensors through exploiting the interesting properties of a new ion-transfer membrane developed at Electrochemical Technology Corp. This membrane is made by copolymerizing methyl methacrylate and a low-concentration acrylic ionogen, either sulfonate or quaternary ammonium. These polymers have exceptionally high transference numbers and good ionic conductivity. Because they are not crosslinked they can be dissolved in certain solvents to make varnishes which can be used to coat ion-transfer films on various devices. Indicator dyes can be incorporated in the varnish to coat optical pH sensors. Neutral carriers can be incorporated to make specific ion electrodes. These devices could satisfy numerous needs in medical research and clinical medicine for microsensors for pH and various cations and anions. Such sensors are potentially inexpensive to make because all needed chemical components can be put into the varnish which is easily applied by dipping and drying.